What happened to that superjumbo?

Debris rained down on the island of Batam yesterday morning after an engine appeared to explode on an Airbus A380 – the world's largest commercial airliner – flown by Qantas. The plane then dumped fuel for 2 hours and made an emergency landing.

Why should I care?

The A380 is one of the aviation industry's latest and most sophisticated aircraft, a computer-controlled carbon-fibre-rich giant that has been in service for only two years. What's more, it can take unprecedented numbers of passengers aloft: the aircraft in this incident was carrying 433, but in an all-economy-class layout, the enormous double-decker plane can transport 800. So a serious problem with an A380 is a matter of great interest to the flying public and the aviation industry alike.

What happened?

Six minutes after the flight took off from Changi airport in Singapore, passengers heard a couple of sharp, loud bangs. They were followed by vibration, smoke and flames, as shards of debris began streaming from the left-side inboard engine. A hole was punched in the wing and engine debris – embarrassingly, in Qantas livery – fell on the nearby island of Batam. One witness told the BBC that fuel was leaking from the crippled engine after landing. In addition, the crew could not immediately shut down the neighbouring outboard engine after landing – implying that debris may also have damaged its control systems.

Do we know the cause?

No. Qantas, engine maker Rolls-Royce of the UK and the Australian Transportation Safety Board are investigating. Rolls-Royce receives a real-time data stream via satellite from each of its engines – supposedly allowing any problems to be diagnosed before they become critical. This data will be invaluable to the investigation.

In the meantime, Qantas has grounded all six of its $340 million A380s. Photos of the wrecked engine show that part of the engine cowling is missing towards the high-pressure rear of the engine. Engine shutdowns are commonplace in commercial aviation – planes can fly with just one – but engine disintegration like that seen yesterday is rare.

But what probably happened?

A jet engine uses a fan to draw in air to a series of compressor turbines. The compressed air enters a combustion chamber where it is mixed with fuel and ignited. Hot ignition gases are then forced out of the back of the engine, turning a high-pressure turbine (HPT) that keeps the fan and compressor turning.

The fan, compressor and turbine all have rotor discs with blades turning at super-high speeds. If a blade breaks off it can shoot out of the engine housing and the hot shards can gouge a hole in the aircraft's fuselage or a fuel tank, risking a fire. Moreover, the loss of the blade unbalances its rotor, causing massive vibration. It's called a "disc burst" or an "uncontained engine failure" – the hole in the wing suggests this is what happened to the Qantas A380.

How is that risk protected against?

The engine cowling cannot protect an aircraft from an uncontained disc or blade failure – the high-speed HPT spins so fast that it is impossible to contain a departing blade. So plane designers make sure that any critical structure that could be hit in an uncontained failure has a backup in another part of the plane.

So the investigation will want to find out how the A380's wing became punctured. A punctured fuel tank in the wing of an Air France Concorde in 2000 led to an in-flight fire and fatal crash.

The lower-speed fan blades at the front of the engine are the ones most likely to come off – when a bird hits them, say – but they turn slowly enough that a reinforced Kevlar band in the fan casing can contain a shed blade.

Have uncontained failures cost lives before?

Yes. In the US in 1989, a United Airlines DC-10 lost all its steering, diving and climbing controls when a burst turbine blade departed the engine casing and severed all the hydraulic pipes in the aircraft's rear fuselage. The pilots had no way to steer the plane but to use the throttles of two remaining engines – and 111 passengers died in the subsequent crash landing at an airport in Sioux City, Iowa.

Could volcanic ash from the current Indonesian eruption have been a factor in the event?

It is certain to be considered by investigators. Ash deposits could make rotor discs unbalanced.

Were the A380's engines tested thoroughly before the plane was allowed into service?

Yes – they have to be. The Trent 900 engines made by Rolls-Royce accumulated 22,000 flying hours before a passenger set foot on the plane.

Has this particular engine run into difficulties before?

Yes. In August, the European Aviation Safety Agency (EASA) ordered airlines to inspect Rolls-Royce Trent 900 engines because some had shown excessive wear on one turbine shaft. Without intervention, the EASA warned, a turbine could slip along its shaft and strike static components. This, says the EASA, could "result in loss of engine performance with potential for in-flight shutdown, oil migration and oil fire… some of these conditions present a potential unsafe condition to the aeroplane".

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